This invention relates to a system employing wind-driven venting for reducing the volatile organics content of soil contaminated by leakage or accidental spill of volatile organics, such as e.g. petroleum hydrocarbons and organic chemicals.
Widespread utilization of petroleum and chemical products in modern society has resulted that these materials are often produced, stored and transported in remote, scarcely populated areas. In such areas, soil contamination from accidental spills and leaks of, e.g. gasoline, can be a problem.
Generally oil and chemicals spilled on undisturbed ground will tend to simply move downwardly under the force of gravity, with some lateral spreading. The rate of movement will depend largely upon the permeability of the soil and the viscosity of the contaminant. Unless the contaminant encounters an impermeable layer or the capillary fringe, i.e. the water saturation zone associated with the water table, downward penetration will continue until the amount of material leaked or spilled is exhausted to immobility. For example, a spill of 100 barrels of gasoline onto a soil having a porosity of 30% will contaminate on the order of 700 cubic yards of soil. If 20% of the gasoline could be removed according to the invention then only about 560 cubic yards would be involved and the depth of penetration may be substantially lessened. This lessening may be particularly helpful where there is a risk of the contaminant reaching the water table, or that soluble components thereof may be leached into the groundwater before natural biodegradation occurs.
Methods for stimulating biodegradation of hydrocarbons in soil and groundwater are known, and described, for example, in U.S. Pat. No. 4,401,569 and U.S. Pat. No. 3,846,290. A method for removing taste spoiling components of oil spilled in a drinking water catchment area is disclosed in U.S. Pat. No. 3,628,607. A method for reducing gasoline vapors from coarse and fine sand is disclosed in American Petroleum Institute Publication No. 4431 relating to forced venting of gasoline vapor. In this procedure air is admitted through sunken vertical pipes having screened holes or slots near the bottom, and is drawn through the porous sand containing the spilled gasoline into one, or a plurality of manifolded-together, sunken exhaust pipes also having screened holes or slots near the bottom, and thence to the suction side of a spark-arrested centrifugal type pressure blower. Such a method would be difficult to apply in less porous soil, and power to operate this type of blower may not be readily available in remote locations. The present invention provides a simple, relatively inexpensive solution to these problems.